WASHINGTON — Attorney General Eric Holder says the fatal shooting of a Mexican teenager by a U.S. Border Patrol agent on the banks of the Rio Grande was "extremely regrettable."

The attorney general told reporters Thursday that the FBI is investigating the shooting of 15-year-old Sergio Adrian Hernandez Huereka on Monday beside a railroad bridge connecting Ciudad Juarez, Mexico, and El Paso, Texas. Holder says the agency also is investigating the death of Anastasio Hernandez, who died Saturday after a U.S. Customs and Border Protection officer shocked him with a stun gun at a border crossing near San Diego.

The two deaths have caused outrage in Mexico.

Holder says that Mexico and the U.S. have shared interests and "that is what will continue to keep this relationship strong."